Crystal oscillators are utilized in many electronic circuits because of their superior stability. However, most crystal oscillators include an active element, such as a transistor, which operates in a non-linear range, such as class B or C amplification. This non-linear device or element introduces harmonics into the output of the oscillator which are very undesirable.
A crystal controlled colpitts oscillator is a typical example of a prior art oscillator wherein a tank circuit is connected to a transistor operating as a class B or C amplifier. The output of the oscillator is generally taken from the collector-emitter circuit of the transistor. Since the transistor is operating in a non-linear mode, harmonics are introduced into the output even though the tank circuit has a relatively pure fundamental frequency therein.